1. Technical Field
The present invention relates to a plasma reactor which generates an active gas including ions, free radicals, atoms and molecules by plasma discharge and performs plasma processing for solid, powder, gas, and the like, using the active gas, and more particularly, to an inductively coupled plasma reactor with multiple magnetic cores.
2. Discussion of Related Art
Plasma discharge is used for gas excitation to generate an active gas including ions, free radicals, atoms and molecules. An active gas is widely used in various fields. Typically, an active gas is used for a semiconductor fabrication process, for example, in various processes of etching, deposition, cleaning, and the like.
A wafer for semiconductor device fabrication or an LCD glass substrate has recently become larger in size. Therefore, a plasma source needs to have high capability of controlling plasma ion energy and to have easy expansibility with capability of processing a large area.
There are many plasma sources for generating plasma. Examples of the typical plasma sources include capacitively coupled plasma and inductively coupled plasma which use radio frequency. It is known that the inductively coupled plasma source is suitable for generating high density plasma because it relatively easily increases ion density as radio frequency power increases.
However, in the inductively coupled plasma, since the energy to be connected with plasma is low than the energy being supplied, a driving coil of a very high voltage is used. Therefore, as the ion energy is high, the inner surface of a plasma reactor is damaged by ion bombardment. The damage of the inner surface of the plasma reactor by the ion bombardment results in negative results of shortening a life of use of the plasma reactor and becoming a cause of contamination in plasma processing. When lowering the ion energy, since the energy connected with plasma is low, plasma discharge is frequently off. Therefore, it is difficult to stably maintain plasma.
In the processes using plasma for semiconductor fabrication, it is known that use of remote plasma sources is very useful. For example, the remote plasma is usefully applied in a cleaning process of a process chamber or an ashing process for photoresist strip. However, as a substrate to be processed becomes larger in size, a process chamber becomes larger in volume. Accordingly, a plasma source needs to be capable of sufficiently remotely supplying a high density active gas. For a multi-process chamber of processing a number of substrates simultaneously, the remote plasma source is increasingly required.